24_header_V1

Performance and Applications of Inertia Based Positioning Drives: Q-Motion

Back to PI Website

Q-motion miniature linear and rotary stages are available in single or multi-axis combinations. Their operating principle is based on the piezo inertia (stick-slip) effect.
Q-motion miniature linear and rotary stages are available in single or multi-axis combinations. Their operating principle is based on the piezo inertia (stick-slip) effect.

Size matters in miniaturization and automation – smaller is usually better. Traditional electromagnetic motors have limitations when it comes to shrinking dimensions while maintaining high efficiency and accuracy of motion with minimized energy consumption. Piezo ceramic inertia motors can fill this gap. The Q-Motion dubbed miniature direct drives can be employed in linear positioners, rotary stages, goniometer cradles, and even 6-axis parallel positioners. In addition to inertia motors, there are many other types of piezo motors, including ultrasonic drives and high-force piezo-walk drives.

Q-motion piezo inertia motors are extremely small. They allow the design or nanometer-precision mechanisms with scaled-down dimensions that were unthinkable a few years ago- ideal for integration into miniaturized instrumentation.
Q-motion piezo inertia motors are extremely small. They allow the design of nanometer-precision mechanisms with scaled-down dimensions that were unthinkable a few years ago – ideal for integration into miniaturized instrumentation.

Stick-slip motors are especially cost-effective and can provide nanometer precision motion if required. They provide the best force/size ratio for smallest dimensions.

Working Principle

A piezoelectric ceramic actuator is preloaded against a moving runner. Controlled by a drive signal with a quasi saw-tooth shape, the actuator expands slowly and contracts rapidly (or in the opposite direction). During the slow expansion, the runner sticks to the coupling element and moves along, while during the rapid contraction, the coupling element slips along the runner, which basically stays in place.

Two different versions were developed optimized either for miniature size, moderate force or compact size and higher force.

1. Tangential Inertia Drive Motor

  • Very Small Dimensions
  • Simple Mechanics
  • To 2 N Holding Force
Watch Stick-Slip Working Principle Video >
Watch Stick-Slip Working Principle Video >

2. Mini-Rod Inertia Drive Motor

Mini-rod stick-slip principle, watch animation >
Mini-rod stick-slip principle, watch animation >

Mini-Rod piezo inertia drives are based on an actuator moving a small rod – or moving along the rod if the rod is fixed. These motors are more powerful than the tangential drives, with up to 10N pushing/holding force. They can be integrated into linear actuators and linear positioning stages, however the principle does not apply to rotary stages.

The operating principle is shown in the animation.

Actuators based on the Mini-Rod drive. N-422 OEM version (left) and N-412 integrated actuator (right) (Image: PI)
Actuators based on the Mini-Rod drive: N-422 OEM version (left) and N-412 integrated actuator (right) (Image: PI)

 

The Q-545 linear positioning stage is based on the mini-rod drive principle. Vacuum version shown left, standard version shown right, 1” travel range. Encoder resolution to 1nm is available. (Image: PI)
The Q-545 linear positioning stage is based on the mini-rod drive principle. Vacuum version shown left, standard version shown right, 1” travel range. Encoder resolution to 1nm is available. (Image: PI)

 

Train of 6nm steps executed with Q-545 closed-loop stage, measured with laser interferometer at 5kHz sampling rate. The highest encoder resolution is 1nm. This type of resolution allows applications in high resolution microscopy. The LPS-45, a predecessor of the Q-545, was used for nanometer precise accurate positioning of the Fresnel Zone Plate along the optical axis of a compact stand-alone EUV microscope [http://onlinelibrary.wiley.com/doi/10.1111/jmi.12494/full] (Image: PI)
Train of 6nm steps executed with Q-545 closed-loop stage, measured with laser interferometer at 5kHz sampling rate. The highest encoder resolution is 1nm. This type of resolution allows applications in high resolution microscopy. The LPS-45, a predecessor of the Q-545, was used for nanometer precise accurate positioning of the Fresnel Zone Plate along the optical axis of a compact stand-alone EUV microscope. (Image: PI)
Multi-axis combination of X-Z linear stage (Q-545), with high-speed U-628 ultrasonic miniature rotary stage. (Image: PI)
Multi-axis combination of X-Z linear stage (Q-545), with high-speed U-628 ultrasonic miniature rotary stage. (Image: PI)

During the stick phase, the runner is moved in the defined direction.

Typical stick-slip cycles (schematic). During the stick phase, the runner is moved in the defined direction. During the slip phase, the runner does not move. The so-called back-stepping effect leads to a small backward motion during the acceleration phase of the piezo actuator. The typical feed- motion per full cycle is 300 nm to 1 µm. It depends on the actuator type and force acting on the actuator. The actuator can be controlled to any position within its range with sub-nm resolution by changing the drive voltage (analog mode).
Typical stick-slip cycles

During the slip phase, the runner does not move. The so-called back-stepping effect leads to a small backward motion during the acceleration phase of the piezo actuator.

The typical feed- motion per full cycle is 300 nm to 1 µm. It depends on the actuator type and force acting on the actuator.

The actuator can be controlled to any position within its range with sub-nm resolution by changing the drive voltage (analog mode).

(left) XY combinations mount directly without adapters. A Z-bracket is available for vertical applications. (right) XYZ motion with combination of Q-521 stages, 12mm and 32mm travel - watch video >
(left) XY combinations mount directly without adapters. A Z-bracket is available for vertical applications.
(right) XYZ motion with combination of Q-521 stages, 12mm and 32mm travel – watch video >

Self-Locking at Rest

As with most piezo motors, Q-Motion inertia drives are self-locking at rest. There is no power consumption, no heat dissipation, no position dither.

Velocity Control

Back-stepping Effect

Between each stick and slip cycle, a miniscule position shift called the back-stepping effect can be noticed. This effect is inseparably connected with the inertia drive principle and its relevance depends on the application.

Q-522.140 with E-871.1A1 controller • Operation Frequency 20 kHz • Data sample rate: 133 kHz • Time base: 0.3 milliseconds, which corresponds to 6 full stick-slip cycles
Q-522.140 with E-871.1A1 controller
• Operation Frequency 20 kHz
• Data sample rate: 133 kHz
• Time base: 0.3 milliseconds, which corresponds to 6 full stick-slip cycles

At a data sample rate of 133 kHz, a backstepping effect is too small to be noticed! Consequentially, we state that the backstepping effect does not influence the constancy and smoothness of velocity. However, there are other factors that directly influence the velocity.

Constancy of Velocity at a Microscopic Level

With the entry level E-871.1A1 motion controller, the selected velocity is reached by adjusting the operating frequency. Adjusting the frequency means that the voltage profile of a single step remains constant with pauses in between. The E-873 controller offers more sophisticated velocity control.

 

Simplified control voltage profile for different operating frequencies
Simplified control voltage profile for different operating frequencies

Other Piezo Motor Drives

Force vs. velocity of different piezoelectric motors
Force vs. velocity of different piezoelectric motors

Comparison of different piezo motors

Comparison of different piezo motors

Lifetime

Lifetime is affected by load, duty cycle, environmental conditions (humidity, vacuum), etc., based on wear motion ranges of >20km are feasible.

Operation Recommendation

Duty Cycles

Ideal applications demand:

  • Duty cycles below 50 %
  • Continuous operating time <10 sec (2x back and forth across the complete travel range)

Product Overview

Linear Stages >

Rotary Stages >

6-Axis Parallel Positioners

In addition to linear and rotary positioners, linear stages can be combined to 6-axis parallel arrangements.

Q-821 6-axis miniature parallel positioner based on Q-521 linear stages compared to ball pen. • 80x80x48 mm³ • 1 nm sensor resolution
Q-821 6-axis miniature parallel positioner based on Q-521 linear stages compared to ball pen.
• 80x80x48 mm³
• 1 nm sensor resolution

 

Q-845 6-axis vacuum positioner based on Q-545 linear stages
Q-845 6-axis vacuum positioner based on Q-545 linear stages

 

Motion Controllers

E-873, 3-channel motion controller

The E-873 3-channel motion controller features:

  • Broadband encoder input
  • Macro programmable for stand-alone functionality
  • Data recorder
  • Nonvolatile EEPROM for macros and parameters
  • Digital I/O ports (TTL)
  • ID chip support
  • Interfaces: TCP/IP and USB
  • Optional digital joystick for manual operation a single channnel version is available as the E-871

 

The E-870 driver features include:E-870 driver • For PIShift and PiezoMike piezo inertia drives • Ideal for OEM applications • One to four actuators, serial control (through demultiplexing) • With digital USB interface • Host software LabVIEW driver included

  • For PIShift and PiezoMike Piezo Inertia Drives
  • Ideal for OEM Applications
  • One to Four Actuators, Serial Control (through demultiplexing)
  • With Digital USB interface
  • Host Software LabVIEW Driver Included

 

 

E-872.01 and E-472.02 OEM driver • Step-direction input signal • E-872.01: full step modus • E-872.02: micro step modus • Cost effective
Download Technical Note for E-872 OEM Driver

Features of the E-872.01 and E-472.02 OEM driver include:

  • Step-Direction Input Signal
  • E-872.01: Full Step Modus
  • E-872.02: Micro Step Modus
  • Cost Effective

 

 

 

 

 

The E-873 Macro programmable specifications include:E-873 Macro programmable • Data recorder • Digital I/ O ports (TTL) • ID chip support • Interfaces: USB, RS-232 and TCP/ IP • Joystick input for manual operation • Velocity control Compatible Sub-D connectors for Q-Motion stages Optionally available with metal-sheet housing for OEM applications.

  • Data Recorder
  • Digital I/ O Ports (TTL)
  • ID Chip Support
  • Interfaces: USB, RS-232 and TCP/ IP
  • Joystick Input for Manual Operation
  • Velocity Control
  • Compatible Sub-D Connectors for Q-Motion Stages
  • Optionally Available with Metal-Sheet Housing for OEM Applications

Vacuum and Nonmagnetic Operation

High-Vacuum to 10-6 hPa

Standard and unprepared Q-Motion stages can be used in ambient conditions and for vacuum up to 10-6 hPa. For vacuum operation, the C-815.VF vacuum feedthrough is available.

 Fig13

On the air side, the following cables will be available for connecting the feedthrough with the controller E-873 (plus adapter cable for E-871, which is included in the delivery of the stage):

Connecting cable available for the feedthrough with the controller E-873

These air-side cables also work for the feedthrough for UHV.

Ultrahigh Vacuum to 10-9 hPa

Ultrahigh vacuum models are also available.

Fig18

Fig15

 Nonmagnetic Operation

PI is currently evaluating ceramic bearings for nonmagnetic stage designs. Nonmagnetic operation is of interest in the environment of electron beam imaging such as lithography or microscopy.

Tests in high magnetic fields

The KIT (Karlsruhe Institute of Technology) has performed tests in high magnetic fields of 9.4 Tesla (T). The stage (not operating) was not attracted by the magnetic field and was not magnetized.

> READ more

> LEARN more about Q-Motion Miniature Stages

> WATCH videos on Different Types of Piezo Motors

precision_motion

Follow the PI Blog!

Enter your email to subscribe and receive notifications of new posts by email.

About PI

PI (Physik Instrumente) is a leading manufacturer of precision motion control equipment, piezo motors, air bearing stages and hexapod parallel-kinematics for semiconductor applications, photonics, bio-nano-technology and medical engineering. PI has been developing and manufacturing standard & custom precision products with piezoceramic and electromagnetic drives for 4 decades. The company has been ISO 9001 certified since 1994 and provides innovative, high-quality solutions for OEM and research. PI is present worldwide with fifteen subsidiaries, R&D / engineering on 3 continents and total staff of more than 1,000.

USA / Canada
www.pi-usa.us | info@pi-usa.us

EAST
(508) 832-3456
MIDWEST
(508) 832-3456
WEST
(949) 679-9191 (LA Area & Mexico)
(408) 533-0973 (Silicon Valley/Bay Area)